The background description provided herein is for the purpose of generally presenting the context of the disclosure. Work of the presently named inventors, to the extent it is described in this background section, as well as aspects of the description that may not otherwise qualify as prior art at the time of filing, are neither expressly nor impliedly admitted as prior art against the present disclosure.
Ignition of a compressed air/fuel mixture in a cylinder of the engine results in combustion. Exhaust gas resulting from the combustion of the air/fuel mixture is expelled to an exhaust system. One or more engine parameters affecting the quantities of air and fuel in the air/fuel mixture may be adjusted based on signals from various sensors that are located in the exhaust system. The temperature of the engine also affects the quantities of air and fuel in the air/fuel mixture. For example, during a cold start of the engine, the air/fuel mixture may be more heavily concentrated with fuel and then become less concentrated as the temperature of the engine increases.